Jet engine combustion processes



Oct. 31, 1961 D. E. CARR 3,006,142

JET ENGINE COMBUSTION PROCESSES Filed Dec. 21, 1959 EXHAUST H '3 NOZZLE IO l5 l6 COMPRESSOR TURBINE AIR INLET l4 Q:

l9 1 FUEL I2 COMBUSTION CHAMBER j 21 INVENTOR.

D. E.CARR

ATTORNEYS United States Patent JET ENGINE COMBUSTION PROCESSES Donald E. Carr, Bartlesville, 0kla., assignor to Phillips Petroleum Company, a corporation of Delaware Filed Dec. 21, 1959, Ser. No. 860,751 17 Claims. (Cl. 6035.4)

This invention relates to the operation of continuous combustion type power plants. In one aspect this invention relates to the operation of jet engines. In another aspect this invention relates to reduction of the smoke density of exhaust gases from a jet engine. In still another aspect this invention relates to the augmentation of thrust in jet engines.

In recent years jet engines have been employed in increasingly large numbers for the purpose of propelling aircraft, particularly military aircraft, and have been found to be highly advantageous in high speed aircraft. In the last few years, said jet engines have been employed in propelling commercial aircraft. With the increase in use of such engines, however, a number of operational problems have been recognized.

Aircraft jet engines can be classified broadly into three general categories or types; turbo engines, e.g., turbo-jet and turbo-prop; ram jet; and pulse jet. The present invention is primarily applicable to the aircraft turbo engines, and is particularly applicable to turbo-jet engines. For this reason and for the sake of brevity the invention will be describedhei ein pri plied to a turbo-jet engine.

A conventional turbo-jet engine comprises three main parts or sections One of those sections is the compressor section. In the compressor section, kinetic energy is imparted to the air stream and is transformed in a diifuser into potential energy as measured by an increase in static pressure in the compressor. Said compressor can be either an axial or a centrifugal compressor. The second part or section, a combustor, is provided to receive compressed air and fuel whicirisburned therein" to increase the temperature of said air and resulting combustion gases within the combustor. Said combustor can be any one of the conventional types, as for example, one that employs multiple combustion chambers (cans) or one that employs an annular combustion tube or chamber. In the can type, the air flow is split upon leaving the compressor section and equal portions are sent to each can, where said portions are combusted with portions of the fuel. The combustion products are then recombined with secondary air and routed to the turbine section. In the annular type of combustion chamber the primary portion of the air is diverted from the main stream and directed toward the fuel injector within said combustion chamber where it burns with the fuel. The remaining or secondary air is then mixed with the products of combustion at a point downstream from the point of introduction of said primary air. The third main part of the engine, the turbine section, is ordinarily provided downstream of the combustor section and receives combustion gases from the combustion chamber. The gas turbine unit in the turbine section receives the gases from the combustor and the power developed by said turbine is employed to drive said compressor and the various auxiliaries of the engine. The remaining energy in the gases exhausted from said turbine is available to propel the aircraft. Thus, forward thrust for the turbo-jet engine is provided by the high velocity jet of gases which emerge from the turbine and which are exhausted through an exhaust nozzle. In a turbo-prop engine, the power developed in the turbine is used to drive the compressea rarieas aa%aiies and aprepeller eetly inter th"e cempressofi kegardi "YOfihfi point and any remaining energy in the gases emerging from the turbine is utilized to provide forward thrust.

Performance of a turbo-jet engine is dependent to a large extent upon the temperature rise which is obtain-able in the engine. Temperature rise is that increase in temperature between the inlet to the combustor and the temperature of the gases at the combustor exhaust outlet. The temperature rise must be carefully controlled, however, for the operation of a turbo-jet engine is limited by the ability of the turbine blades to withstand high temperatures. Fuel which is supplied to the combustor is burned in the presence of supplied air and raises the temperature of the combustion gases and unused air by the heat of combustion. An excess of air is conventionally utilized to control the temperature of the gases contacting the turbine blades. The hot gases are expanded through the turbine section which provides power for the compressor as mentioned above. Further expansion takes place in a rearwardly extending exhaust nozzle to provide a substantial increase in gas velocity. The thrust which is provided by the engine equals the gas mass flow to the exhaust duct times its increase in speed according to the law of momentum. As mentioned above, the temperature rise which is obtained in the engine must be carefully controlled and is limited by the ability of the turbine blades to withstand high temperatures. This enforced control of temperature rise creates operational problems, particularly at takeeti' ender high alead wmd adnring ememgency"can ditions in flight when an abnormally large increase in developed thrust is necessary. Generally speaking, approximately fifty percent more power or thrust is required at takeofi than is required under normal cruising conditions. This large amount of thrust required at takeoff, and the necessity for providing extra power or thrust for emergency conditions which occur in flight, has presented serious problems for engine designers and manufacturers. Obviously the greater load which can he liftedat rakeerr renders operation of the aircraft more profitable in commercial operations and more effective in military operations. Just as obvious, however, there is a point of economic balance as well as weight balance. In general, it is not economical or practical to equip an aircraft with excessively large engines, or an excessive number of engines, in order to be able to lift maximum load at takeoff and then employ a reduced number of said engines, or only about fifty to sixty percent of the available power of the engine, at cruising speed.

To overcome this problem present day turbo-jet engines have been designed to operate with the injection of a power augmentation or thrust augmentation liquid at takeoff, and in emergency conditions which may develop in flight. These thrust augmentation liquids serve to lower the temperature of the gases exhausted from the combustion chamber before said gases enter the turbine section and thus make it possible to burn more fuel without exceeding a maximum temperature for said exhaust gases. Thrust augmentation liquids such as water, and mixtures of methyl alcohol or ethyl alcohol with water, are conventionally injected into the compressor inlet or into the combustion chamber of a jet engine. The use of isopropyl alcohol-water mixtures as thrust augmentation liquids has been suggested. Said thrust augmentation liquids can be injected into the air inlet upstream of the compressor, into the compressor itself, into the diffuser downstream of the compressor and upstream of the combustion chamber, or directly into the combustion chamber. As discussed hereinafter, it is usually preferred to inject the thrust augmentation liquid of injection, said liquids by being vaporized extract heat and thus act to cool the gases entering the turbine section, thereby permitting more fuel than normal to be burned within the combustion section without exceeding the maximum temperature limits which can be tolerated within said turbine section. It has been found that a 24 percent increase in thrust can be realized with water injection in a centrifugal machine, but the increase is obtained at a very high specific liquid consumption. Water-ethanol injection tests on an axial flow compressor turbo-jet have shown an increase of 12-16 percent in thrust. The higher value was obtained with water injection at the compressor inlet, the lower value was obtained with water and ethanol injected into the combustion chamber.

While the prior art use of water and said alcoholwater mixtures, such as ethanol-water mixtures, augments the thrust developed by the engine, the use of such liquids has created other problems and leaves much to be desired. The use of said alcohol-water mixtures results in excessive smoke and a general combustion dirtiness. The problem of increased smoke in the exhaust gases, measured as an increase in smoke density, is serious; particularly in those localities afllicted with smog problems or fog problems. Indeed, the problem has become so severe in some localities that local authorities have required that the smoke density be lowered to acceptable values or the operation of the jet aircraft be suspended. Furthermore, not only is a nuisance created insofar as the locality immediately surrounding the airport is concerned, the thick clouds of smoke which are ejected are a hazard to operation of the airport itself and to other planes operating in and out of the airport. Thus the problem of excessive smoke in the exhaust gases has become more critical and of more importance than the problem of thrust augmentation.

Solving the problem of thrust augmentation is of little or no value from a practical standpoint if in solving said problem there is created or left unsolved another more critical problem. This is what has happened in the prior art. Water alone was an early thrust augmentation liquid. As is well known, Water serves very well to augment thrust but it also greatly increases the amount of smoke in the engine exhaust gases. The water-alcohol thrust augmentation mixtures (using the above mentioned prior art normal and iso alcohols) are only slightly better than water alone with respect to the amount of smoke in the engine exhaust gases. Jet engine manufacturers, aircraft manufacturers, and fuel manufacturers are all searching diligently for some means for reducing the amount of smoke in the engine exhaust gases.

I have now found that a mixture of a C to C saturated aliphatic alcohol and a C to C parafiin hydrocarbon, when admixed with water, not only forms a good thrust augmentation liquid but is also an excellent smoke suppression agent in that it very markedly reduces the amount of smoke in the engine exhaust gases. It was surprising and unexpected to find that said admixture comprising water, said alcohol and said hydrocarbon is a much better smoke suppressing agent than either of (1) a mixture comprising water and said alcohol or (2) a mixture comprising water and said hydrocarbon. Thus a synergistic effect is obtained when said alcohol and said hydrocarbon are used in combination together with water in said admixture.

Said admixture accomplishes at least two improvements in the operation of jet engines; 1) acts as a coolant for the gases exhausted from the combustion chamber and thus augments thrust by permitting more fuel to be burned in said combustion chamber; and (2) decreases the smoke density of the gases exhausted from the engine.

Thus, broadly speaking, my invention resides in a new smoke suppressing and thrust augmentation agent comprising water, said alcohol, and said hydrocarbon, and

in a method of operation of an aircraft turbo engine which method comprises introducing said thrust augmentation and smoke suppressing agent into a combustion zone of said engine.

By the term thrust augmentation, augmentation of thrust, or to increase thrust, or the like, there is meant an increase in thrust obtained from use of a supplementary or auxiliary apparatus or operation over the thrust obtained without use of such supplementary or auxiliary apparatus or operation.

By the term specific thrust is meant the pounds of force exerted on the craft per pound of air used in the combustion of the fuel.

An object of the invention is to provide an improved method of operating an aircraft turbo engine. Another object of the invention is to provide a method for reducing the smoke density of the gases exhausted from an aircraft turbo engine. Another object of the invention is to provide a method for augmenting the thrust developed by an aircraft turbo engine. Still another object of the invention is to provide an improved smoke suppressing and thrust augmentation mixture for use in aircraft turbo engines. Other aspects, objects and advantages of the invention will be apparent to those skilled in the art in view of this disclosure.

Thus according to the invention there is provided as a smoke suppressing and thrust augmentation liquid or agent, an admixture comprising from about 10 to about 90 weight percent of water, from about 90 to about 10 Weight percent of a mixture consisting essentially of synergistic proportions of a saturated aliphatic alcohol containing from 1 to 4 carbon atoms per molecule and a parafiin hydrocarbon containing from 5 to 12 carbon atoms, and a small but effective amount of an emulsifying agent.

Further according to the invention there is provided a method of operating an aircraft turbo engine, which method comprises: the step of introducing said admixture into a combustion zone of said engine.

Alcohols which can be used in the practice of the invention are the low molecular Weight saturated aliphatic alcohols containing from 1 to 4 carbon atoms per molecule Examples of said alcohols are methanol, ethanol, isopropanol, and tertiary butanol.

Hydrocarbons which can be used in the practice of the invention are the C to C paraflin hydrocarbons. The term paraffin hydrocarbons is used generically herein and in the claims and, unless otherwise specified, includes normal parafiins, isoparalfins, and cycloparaflins. The cycloparaflins containing from 6 to 10 carbon atoms per molecule are the preferred cycloparaflins. The most preferred hydrocarbons are the C to C normal paraflins because they possess very clean burning characteristics and good volatility characteristics.

As will be shown in the examples given hereinafter, when at least one of said saturated aliphatic alcohols and at least one of said C to C parafiin hydrocarbons are used together there is obtained a synergistic effect. Thus, in the practice of the invention, said alcohols and said hydrocarbons are used together in a mixture in synergistic proportions. It is generally preferred that said mixture contain from 20 to volume percent of at least one of said alcohols and 80 to 20 volume percent of at least one of said hydrocarbons. More preferred ranges are 40 to 60 volume percent alcohol and 60 to 40 volume percent hydrocarbon.

Said mixture of at least one of said alcohols and at least one of said hydrocarbons is used in admixture with water and an emulsifying agent. The resulting admixture which forms the smoke suppressing and thrust augmentation liquid of the invention ordinarily can contain from about to about 10 weight percent water and from about 10 to about 90 weight percent of said alcohol-hydrocarbon mixture. More preferred proportions are 90 to 50 weight percent water and 10 to 50 weight injection at this point reduces the capacity of the compres percent of said alcohol-hydrocarbon mixture. s'or.' Injection directly into the compressor is the most In the practice of the invention an emulsifying agent preferred point of injection. When injected into the is used so as to form a stable emulsion of the water, hycompressor, said smoke suppressing and thrust augmenta: drocarbou, and alcohol. The emulsifying agent per se 5 tion liquid is introduced at some intermediate stage of forms no part of my invention. Any emulsifying agent compression, preferably at a point where favorable intercapable of forming an oil-in-water emulsion or a watercooling occurs. Introduction directly into the compressor in-oil emulsion can be used. Thus any suitable emulsifyis preferred because when so injected said liquid cools ing agent can be used in the practice of the invention. the air as it is being compressed and thus acts as an inter- The ashless emulsifying agents armprefenred because aaeetnen eempreeeer greetly'iacreaeiag the 'ea- We a on burning no inorganic solids are formed which possibly pacity of said compressor. As will be understood by could cause deposits in the engine and/ or on the turbine those skilled in the art, an increase in the capacity of blades. Said ashless emulsifying agents burn and/or dethecompressor will ultimately result in more available compose to products not contibutingntonmnkenproduch fllst fronntheenglnebecau -merefaia at a l .i'er te' a tion and are preferred for this reason also. However, perature, is available to permit the burning of more fuel emulsifying agents having an ash content can also be used in the combustion chamber. with good results in the practice of the invention. The advantages of the invention can also be realized by The amount of emulsifying agent used in the practice injection of the smoke suppressing and thrust augmentaof the invention will depend upon the particular emulsifytion liquid into the difiuser downstream of the compressor ing agent used as will be understood by those skilled in the or directly into the combustion chamber because introact. Suflicient emulsifying agent is used to give a stable duction at these two points will also result in cooler exemulsion. The amount used will generally be within the haust gases from said combustion chamber for introducrange of 0.1 to 5 preferablyQlto neight percent ei fion into tlae tnrbine seetien." fieweven einee the smek the total admixture. suppressing and thrust augmentation liquid is introduced Emulsion stability is measured in terms of the amount downstream of the compressor, the advantage of the inof liquid which separates from the emulsion upon standcreased capacity of the compressor .as discussedabove is ing at a given temperature for a given period of time. As sacrificed. For these reasons, the latter two points of used herein a stable emulsion is defined as one having introduction are less preferred than injection of said liquid not more than one percent liquid separation upon standdirectly into the compressor. i ing one hour at 75 F. Obviously the stability of the Regardless of the place of injection of the smoke supemulsion can be varied Within wide limits, as desired, depressing and thrust augmentation liquid, 7 said .liquid is pending upon the amount of and the particular emulsifyultimatelyintroduced into the combustion chamber, the ing agent used. exhaust gases from saidpombustion chamber are cooled;

As will be recognized by those skilled in the art there and the smoke density of said exhaust gases is caused to are a great many emulsifying agents which can be used be decreased; In'the practice of the invention said liquid in the practice of the invention to form emulsions havis introduced into said combustion chamber in an amount ing the stability set forth above, or an even greater stabilsufficient to appreciably augment the thrust of the engine ity. Due to this fact, and since the smoke suppressing and sufficient to appreciably reduce the smoke density of and thrust augmentation liquids of the invention are the exhaust gases from said engine. The actual amount readily prepared in conventional vessels equipped with 40 of said liquid introduced into said combustion chamber conventional mixing devices, wherein the liquid can be will vary depending upon the design of the specific engine, reemulsified if necessary, emulsion stability is no problem. operating conditions such as the altitude at which the in the practice of the invention. engine is operating, the length of runway available, the

Examples of suitable emulsifying agents which can be load carried by the aircraft the engine is propelling, and used in the practice of the invention include, among other factors as will be understood by those skilled in the others, the following: polyoxyethylene sorbitan monoart. Therefore the invention is not limited to the introlaurate (Tween 20); polyoxyethylene sorbitan monooleate duction of any specific amount of the smoke suppressing (Tween 60); polyoxyethylene sorbitan trioleate (Tween and thrust augmentation liquids (coolants) of the inven- 85); sorbitan monolaurate (Span 20); sorbitan monotion. Said liquid (coolant) is usually introduced in an oleate (Span 60); 1-hydroxyethyl-2-heptadecenyl glyamount sufiicient to give a coolant to air weightratio oxaldine (Amine 220); trihexyl sulfotricarbyllate (Nekal Within the range of about 0.001 to about 0.15. In many NS); sulfonated tallow (Napco 1497B); 80/20 copolymer instances it is preferred that said ratio be in the range of lauryl methacrylate-diethylaminoethyl methacrylate; of about 0.001 to about 0.10 or a more narrow range, sodium lauryl sulfate; ammonium lauryl sulfate; butylsuch as from 0.01 to about 0.07. However, with some amine salt of di-hexyl-4-sulfophthalate; rnercaptan-ethylengines under some conditions said ratio can go as high ene oxide condensation products;phenelwtkiylenemnide aslii er aiglaera fl hen mid liquid (eeelant}%e intre condensation products such as the condensation product duced directly into the primary combustion portion of of nonyl phenol with four mols of ethylene oxide (Igepal the combustion chamber it is usually preferably intro- Co430); and duomeen-T-dioleate (N-alkyl-trimethyleneduced in an amount suflicient'to give a coolant to air diamine). Weight ratio within the range of from about 0.001 to about The invention will be further described as applied to 0.10. It is within the scope of the invention to inject a turbo-jet aircraft. However, it is to be understood that portion of saidliquid'into the primary portion of the the invention has application to any type of aircraft combustion chamber and another portion into the secondturbo engine such as turbo-jet, turbo-prop, or turbo-propary portion of the combustion chamber. Thus, a suitable et. 5 overall range of injected smoke suppressing and thrust The attached drawing is a diagrammatic illustration of augmentation liquid is an amount sufiicient to give a the functional portions of a turbo-jet engine. smoke suppressing and thrust augmentation liquid to air In the practice of the invention, the smoke suppressingv ratio within the range of about 0.001 to about 0.2.

an' dthrust augmentation liquidtcoolant) man he iniectedzzngleferrmgnttwitonsaididrawlngnhe invemmniuilllrhew into (a) the air inlet to the compressor, (b) directly more fully explained. Since the operating cycle and the into the compressor, (c) the diifuser, i.e., downstream elements of a conventional turbojet engine arewell known of the compressor and upstream of the combustion chamto those skilled in the art, the fuctional parts of a turboher, or (d) directly into the combustion chamber. Of jet engine have been illustrated diagrammatically. In

these possiblepoints of injection, injecfioniintonheinle k :haiving thereis illusuatedaa ornpseseer meas 11 a of the compressor is usually the least preferred because having an air inlet means 10 for the introduction'of air into said compressor means. In said compressor the air is usually compressed to a pressure within the range of about 4 to 12 atmospheres. From the compressor, the compressed air flows into combustion section 12 where it is combined with a metered, and atomized or prevap-orized, amount of fuel introduced via conduit 22 and its temperature increased by combustion of said fuel. From said combustion section 12 the exhaust gases comprising combustion products and excess air flow to turbine 13 which may contain one or more turbine rotors and one or more stages. Said gases entering said turbine section cause the turbine rotor or rotors to revolve and to drive the compressor in said compression section by means of shaft means 15 which connects the compressor in said compression section and the turbine in said turbine section. The gases exhausted from said turbine section then flow through tail pipe section 14 and are vented to the atmosphere through exhaust nozzle 16.

In the practice of the invention, the smoke suppressing and thrust augmentation liquid (coolant) of the invention can be introduced into the inlet of the compression section 11 by means of conduit 17; directly into the compressor in said compression section by means of conduit 18; into the diffuser downstream of said compression section and upstream of said combustion section 12 by means of conduit 19; or directly into said combustion section 12 by means of conduit 21. Any suitable conduit means and injection means can be employed for injecting said liquid at the above mentioned p aces.

The following example will serve to further illustrate the invention.

EXAMPLE A series of test runs was carried out in a 2-inch diameter fuel atomizing combustor embodying features common to full scale turbo-jet combustion systems. Said combustor comprises a perforated flame tube closed at its upstream end and mounted within an outer shell to provide an annular air flow space between said flame tube and said shell. Said annular air flow space is closed at its downstream end so as to cause air to enter said flame tube through said perforations. The ratio of primary combustion air to secondary quench or diluent air is about 1 to 4, based on the area of the perforations in the upstream and downstream portions of said flame tube. Fuel is injected into said flame tube through an atomizing nozzle actually positioned in the upstream end thereof. Some air is admitted around the fuel spray nozzle in a swirling pattern to assist atomization of the fuel.

In said series of test runs the primary fuel used was a J P-4 referee fuel having the properties set forth in Table I below, or normal heptane. In said test runs the various liquids (coolants) to be tested were injected at various coolant to air weight ratios into the air stream downstream from the compressor and upstream from said combustor a suflicient distance to permit complete vaporization of said liquid prior to entry into said combustor.

Average operating conditions of the combuster during each of said test runs were as follows:

Inlet air pressure 300 inches Hg Abs. Inlet air velocity 100 feet per second. Inlet air temperature 600 F.

Exhaust gas temperature 1300 F.

Said exhaust gas temperature was maintained essentially constant at 1300 F. for each test run by varying the fuel to air weight ratio within the limits of about'0.010 to about 0.02 to compensate for the amount of coolant injected.

During said test runs the amount of smoke in the combustor exhaust gases was determined by measuring the smoke density of said gases. The results of these measurements are shown in Table II below. Said smoke density measurements were made with an E. K. Von

8 Brand continuous gas sampling filtering recorder. The filter paper strips from said Von Brand recorder were evaluated with a Welch Densichron reflection head densitometer which rated said strips between 0 and 100 per cent according to blackness.

Some of the properties of the JP-4 referee fuel used as a primary fuel in some of the above described test runs are given in Table I below. Said fuel conformed with JP-4 specifications in every respect.

Table l PROPERTIES OF .TP-4 REFEREE FUEL API gravity 49.0 ASTM distillation, F

IBP 141 EP 514 Parafiins+naphthenes-LV percent 78.1 Aromatics-LV percent 19.6 Olefins-LV percent 2.3

Table II EFFECTIVENESS OF OOOLANTS IN REDUCING SMOKE DENSITY Smoke density for water alone minus the smoke density for various coolant mixtures, Percent Coolant to 74.25 wt. per- Primery Fuel Air-Wt. 75 wt. cent Water, 80.2 wt. per- Ratio percent 12.5 wt. percent Water,

Water, cent, n-C1, 18.5 wt. per- 25 wt. 12.5 wt. percent 11-01, percent cent Ethanol, 1.3 Wt. per- Ethanol 0.75 wt. percent EA.

cent a.

JP-4 Referee"... 0. 04 4 14 1 0.06 5 38 8 0. 04 12 20 9 n-Heptane. 0. 06 17 29 19 l ethanol, 5% water. 2 E.A.=emulsifying agent (55 wt. percent Tween 2045 wt. percent Span 20).

From the above data is is evident that a synergistic effeet is obtained when an alcohol and a hydrocarbon are used together in the smoke suppressing and thrust augmentation liquid of the invention. For example, when using the n-heptane primary fuel and a coolant to air weight ratio of 0.04 the amount of smoke in the combustor exhaust gases was '(a) only 12 percent less when using the 'water ethanol mixture than when using water alone, ('17) was a surprising 20 percent less when using the water-normal heptane-ethanol mixture of the invention than when using water alone, and (0) only 9 percent less when using the water-normal heptane mixture than when using water alone.

Any suitable type of hydrocarbon fuel can be employed in the practice of the invention. Said fuels which can be so employed include the conventional jet engine fuels which comprise a blend of hydrocarbons boiling in the 'range from about to about 700 R, such as gas oils, kerosene, and gasolines, including aviation gasoline. Fuels of the paraflin and naphthenic type having relatively low aromatic content, i.e., not more than about 20 liquid volume percent aromatics, as well as fuels of the automatic type having high aromatic contents ranging from about 20 up to about 88 percent or higher liquid volume percent aromatics, can be used in operating continuous combustion turbo type aircraft engines according to the practice of the invention. Hydrocarbon fuels having wide boiling range, such as JP-3, JP-4, or fuels of the kerosene type, such as JP-S, can be employed, the boiling range of these fuels generally being in the range of about 200 to about 600 F.

Hydrocarbon fuel and air are injected into the combustion zone of jet engines at a fuel to air weight ratio between 0.005 to 0.10. Turbo-jet engines are preferably operated on an overall fuel to air weight ratio between 0.01 and 0.03. In the practice of this invention, hydromixture comprising: from to 90 weight percent of carbon fuel and air are injected into the combustion zone water; from 90 to 10 weight percent of a mixture conof the engine at a fuel to air Weight ratio between 0.005 sisting essentially of from 20 to 80 volume percent of a to 0.10. The exact fuel to air ratio which it utilized will saturated unsubstituted aliphatic alcohol containing from depend upon engine design limitations, such as turbine 1 to 4 carbon atoms and from 80 to 20 volume percent of durability and the like, as will be understood by those 10 a paraflin hydrocarbon containing from 5 to 12 carbon skilled in the art. The air supplied to the turbo-jet engine atoms; and a small but effective amount of an emulsifying will generally have an air inlet pressure between about 40 agent. and about 500 inches of mercury absolute and will have i 2. In the method of operating a turbo aircraft engine a linear air velocity of from about 30 to about 200 feet wherein air is introduced into and compressed in a comper second. The fuellsupply to the combustor will have 15 pressor, the resulting compressed air is introduced into a temperature of between about 60 F. and about 350 a combustion chamber of said engine, a liquid hydro- F. The air is usually supplied to the combustqr at a temcarbon fuel is introduced into said combustion chamber perature between about 30 F. and about 900 F., and burned with a portion of said air to form a mixture more frequently between 100 F. and 760F. Fuel inof combustion gases and air, said mixture is exhausted jection temperature will be dependent upon fuel characfrom said combustion chamber through a turbine and out teristics such as freezing point and-volatility as well as of an exhaust duct to impart thrust to said engine, the injection nozzle characteristics. improvement which comprises introducing into said com- When a turbojet engine is developing its maximum bustion chamber, as a smoke suppressing and thrust augrated thrust with normal operation, it is operating with mentation liquid, and in a liquid to air weight ratio Witha maximum allowable turbine inlet temperature and maxin the range of 0.001 to 0.2, an admixture comprising: imum rotor speed. Since the rotor speed determinesfl he =from-lfi te o weight pereent oi avatere'fre 7 F90 &319 7 pressure ratio of the compressor, the compressor is thus weight percent of a mixture consisting essentially of from operating with its maximum pressure ratio. Conse- 20 to 80 volume percent of a saturated unsubstituted aliquently, means for augmenting the thrust of the engine phatic alcohol containing from 1 to 4 carbon atoms per must be based upon means which do not increase the molecule and from 80 to 20 volume percent of a paraifin turbine inlet temperature or the compression ratio. hydrocarbon containing from 5 to 12 carbon atoms per The thrust developed by a turbojet engine is a function molecule; and from 0.1 to 5 weight percent of an emulsiof the mass rate of flow of air and fuel and of the difi'erfying agent. ence between the velocity of the jet and the craft being 3. The method of claim 2 wherein said admixture is inpropelled thereby, as indicated by the following formula: jected into the inlet of said compressor, along with said ThrustzG V) 2.582131 passes to said combustion chamber along with g 4. The method of claim 2 wherein said admixture is in which Gzmass rate of flow of air and fuel, as in injected into andutermediate stage of said compressor pounds Per second; gzthe acceleration due to gravity in 40 and passes to said combustion chamber along w1th sald feet per second; V-=velocity of the jet in feet per second V=the velocity of the craft, also in feet per second. For of dam 2 WhQFem Sald admlxture 1S a given flight speed V, the thrust of the engine can b in ected into said compressed air stream downstream increased by increasing V the velocity of the jet, or by from but Elpstream 9 sald combustlon 9 increasing G, the mass rate of flow of the air and fuel, or Passes 52nd combustlol} Chamber along W1th i both V1 and 6. The method of claim 2 wherein said admixture 18 With the use of the water-hydrocarbon-alcohol mixinlected dimcfly into Said combusilon 1131110613 tures of the invention, the value of G for a given turbine n the Operation of a turbo alrcraft 9 Wherem inlet temperature is increased, thereby increasing engine a liquld hydrocarbon filfil and are burned a P thrust, d h amount f smoke i h engine exhaust bustion zone of said engine, a thrust augumentation liquid gases i markedly d d, is introduced into said combustion zone, and resulting The following gives exemplary operating conditions of gases are exhausted from said engine so as to impart the apparatus of the drawing from the air inlet to the exthrust thereto, the method of reducing the smoke density haust nozzle: of said exhaust gases which comprises introducing into 55 said combustion chamber as a smoke suppressing and Compressor Compressor Combustion thrust augmentation liquid an admixture comprising: Inlet at Chamber Outlet from 10 to 90 weight percent of water and from 90 to 10 Weight percent of a mixture consisting essentially of from fig ggf fis gggfi g atmwpheres' 20 to 80 volume percent of a saturated unsubstituted ali- Mass of air lpo lpm phatic alcohol containing from 1 to 4 carbon atoms per molecule and from 80 to 20 volume percent of a paraffin The temperature of the gases leaving the combustion hydrocarbon containing from 5 to 12 carbon atoms per chamber will, of course, vary with the fuel composition, molecule; and from 0.1 to 5 weight percent of an emulsiand with the proportion of combustibles (alcohol and f i agent hydrocarbon) in the coolant mixtures of the invention. 8. The method of claim 2 wherein Said admixture b i'f collflbusfibles content the hlgher 15 the comprises from 90 to 50 weight percent of water and com us 1011 empera ure.

While certain embodiments of the invention have been 323 11 13 ig g fg gg sald mixture of Sald para y ocar on. descnbed for illustrative purposes, the invention obviously 9 Th th d f 1 8 h d t is not limited thereto. Various other modifications will 6 me o o c m w erem Sal a mix um 15 be apparent to those skilled in the art in view of this disclosure. Such modifications are within the spirit and scope of the invention.

I claim:

wherein air and a liquid hydrocarbon fuel are burned in a combustion zone of said engine and resulting gases are exhausted from said engine so as to impart thrust thereto, the step of introducing into said combustion zone an -adintroduced into said combustion chamber in a smoke suppressing and thrust augmentation liquid to air weight ratio within the range of 0.001 to 0.15.

10. The method of claim 8 wherein said admixture is introduced into said combustion chamber in a smoke suppressing and thrust augmentation liquid to air weight ratio within the range of 0.001 to 0.1.

11. The method of claim 8 wherein said admixture is introduced into said combustion chamber in a smoke suppressing and thrust augmentation liquid to air weight ratio within the range of 0.01 to 0.07.

12. The method of claim 2 wherein: said alcohol is selected from the group consisting of methanol, ethanol, isopropanol, and tertiary butanol; and said paraflin hydrocarbon is a. normal paraflin hydrocarbon containing from 7 to 10 carbon atoms.

13. The method of claim 2 wherein said alcohol is ethanol and said hydrocarbon is normal heptane.

14. As a smoke suppressing and thrust augmentation liquid, an admixture comprising: from 10 to 90 weight percent of water; from 90 to. 10. Weight percent of a mixture consisting essentially of from 80 to 20 volume percent of a saturated unsubstituted aliphatic alcohol containing from 1 m4 carbon atoms per molecule and from 20 to 80 volume percent of a paraffin hydrocarbon containing from 5 to 12 carbon atoms per molecule; and from 0.1 to 5 weight percent of an emulsifying agent.

15. The smoke suppressing and thrust augmentation liquid of claim 14 wherein said emulsifying agent is present in said admixture in an amount of from 0.1 to 5 Weight percent.

16. The smoke suppressing and thrust augmentation liquid of claim 14 wherein: said alcohol is selected from the group consisting of methanol,ethanoLisopropanol, and tertiary butanol; and said hydrocarbon is a normal paraffin hydrocarbon containing from 7 to 10 carbon atoms.

17. The smoke suppressing and thrust augmentation liquid of claim 14 wherein: said alcohol is ethanol; and said hydrocarbon is normal heptane.

References Cited in the file of this patent UNITED STATES PATENTS Kolfenbach et a1. Feb. 26, '1957 Kosmin Feb. 10, 1959 

1. IN THE METHOD OF OPERATING AN AIRCRAFT TURBO ENGINE WHEREIN AIR AND A LIQUID HYDROCARBON FUEL ARE BURNED IN EXHAUSTED FROM SAID ENGINE SO AS TO IMPART THRUST THERETO, THE STEP OF INTRODUCING INTO SAID COMBUSTION ZONE AN ADMIXTURE COMPRISING: FROM 10 TO 90 WEIGHT PERCENT OF WATER, FROM 90 TO 10 WEIGHT PERCENT OF A MIXTURE CONSISTING ESSENTIALLY OF FROM 20 TO 80 VOLUME PERCENT OF A SATURATED UNSUBSTITUTED ALIPHATIC ALCOHOL CONTAINING FROM 1 TO 4 CARBON ATOMS AND FROM 80 TO 20 VOLUME PERCENT OF A PARAFFIN HYDROCARBON CONTAINING FROM 5 TO 12 CARBON ATOMS, AND A SMALL BUT EFFECTIVE AMOUNT OF AN EMULSIFYING AGENT. 